The present invention relates to a remote controlled closed circuit television monitoring system, and in particular to a monitoring system that is adapted to low-light level operation.
A major problem with previous monitoring systems of this type concerns the life of the light intensifier, which is used to enhance or increase the light received at the camera lens during night operation. Due to the sophisticated technology involved, the cost of the light intensifier constitutes a significant portion of the total cost of the system. In many monitoring systems, a single camera is employed and the light intensifier is permanently affixed or glued to the face of the camera. Thus, the intensifier will be utilized any time the camera is operational, day or night. It is also apparent that when the intensifier needs to be replaced, the television camera must also be replaced. In other single camera systems where the intensifier is not directly attached, a motorized mirror or other similar devices must be employed in order to remove the intensifier from the path between the lens and camera for day operation.
Another factor affecting the life of the intensifier is the amount of light entering the intensifier. An overload situation may occur if the ambient light intensity is beyond an acceptable limit for the light intensifier. This situation has been controlled previously with neutral density filters and lens iris control, or with manual intensifier gain control.
Regarding the transmission of control signals to the television camera, an inherent shortcoming in previous systems concerns the distance range available between the transmitter unit and receiver unit. In many systems, a power supply is contained in the transmitter unit, and a separate wire is supplied for each control signal to be transmitted to the receiver. Due to the number and gauge of the wires involved and the sensitivity of the relays in the receiver unit, the distance between the transmitter and receiver is quite limited. This result is counter to the purposes of a remote controlled television monitoring system.